Re: [PATCH v4 4/7] sched/fair: remove useless check in select_idle_core

[Abel Wu]

On 6/28/22 7:42 AM, Josh Don Wrote:
> On Sun, Jun 19, 2022 at 5:05 AM Abel Wu <wuyun.abel@xxxxxxxxxxxxx> wrote:
> > The function only gets called when sds->has_idle_cores is true which can
> > be possible only when sched_smt_present is enabled.
> >
> > Signed-off-by: Abel Wu <wuyun.abel@xxxxxxxxxxxxx>
> > ---
> >   kernel/sched/fair.c | 3 ---
> >   1 file changed, 3 deletions(-)
> >
> > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> > index aba1dad19574..1cc86e76e38e 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -6256,9 +6256,6 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
> >          bool idle = true;
> >          int cpu;
> >
> > -       if (!static_branch_likely(&sched_smt_present))
> > -               return __select_idle_cpu(core, p);
> > -
>
> The static branch is basically free; although you're right that we
> currently don't take !smt_present branch direction here, it doesn't
> seem harmful to leave this check in case assumptions change about when
> we call select_idle_core().

I was thinking that it would be better to align with select_idle_smt
that the caller do the check if necessary.

> >          for_each_cpu(cpu, cpu_smt_mask(core)) {
> >                  if (!available_idle_cpu(cpu)) {
> >                          idle = false;
> > --
> > 2.31.1